Modern vehicles typically have one or more diagnostic systems, generally having separate computer control modules or electronic control units (ECUs) to control various functions of the vehicle. Some examples include powertrain control module (PCM), engine control module (ECM), transmission control module (TCM), anti-locking brake system (ABS), and an air bag control module. The vehicle diagnostic systems often have self-diagnostic capability to detect and alert the driver of problems the vehicle may be encountering. When a problem is found, a diagnostic trouble code or DTC, is set within the computer's memory. DTCs are as general or as specific as the manufacturer desires.
To retrieve and decipher DTCs, an auto repair technician needs a diagnostic tool, such as a scan tool. The scan tool must, therefore, be connected to the vehicle's data link connector (DLC) to access and retrieve the DTCs. Scan tools are testing devices that interface with the vehicle's diagnostic systems to retrieve information from the various control modules. The scan tools are equipped to communicate in various communication protocols such as Controlled Area Network (CAN), J1850 VPM and PWM, ISO 9141, Keyword 2000 and others. These communications protocols are specific to the various automobile manufacturers.
A cable is used to interface the scan tool with the DLC. Although the DLC typically is a J1960 type connector having 16 pins for various communications, controls and measurements, the use of the different pins for different functions varies between the different modules in the vehicle and can also vary with different manufactures of the vehicles. Thus, a maintenance garage would need to carry different cables configured for the various pin configurations and communication protocols used by various vehicle manufacturers. Additionally, the garages can carry different “keys” or smart system interface (SSI) that can be individually configured for a certain vehicle or communication protocol. These solutions are problematic in that they require the garage to carry various cables or keys for the various vehicles being serviced and require the technician to know which cable or key goes with which vehicle under service. Additionally, the cables and keys can get lost because there are so many to keep track of in the garage.
The J1962 connector also supplies the ground signal to the scan tool so that the scan tool can use that as a reference signal. Without a good ground signal, the measurements received by the scan tool may not be accurate. The ground signal can be from a chassis ground or from a signal ground. However, some vehicles do not supply both so that receiving a reference signal can be difficult.
Accordingly, it is desirable to provide an adaptive cable that is configurable between a diagnostic scan tool and a DLC. It is also desirable to provide the adaptive cable with a relay that can switch from a signal ground to a chassis ground or vice versa depending on which ground is available in order to for the scan tool to record accurate measurements.